In order to improve passenger comfort, a large number of seats are provided with electrical actuation devices allowing modification of the configuration of the seat by movable portions thereof being moved.
For example, such a seat comprises an inclinable backrest and a legrest, each articulated to an end of a seat portion, the legrest is generally extended by a sliding footrest. They are each moved by an individual actuator. Sometimes, the seat itself can move in its entirety in relation to the fixed base of the seat under the control of an actuator.
When some portions of the seat strike obstacles, that may lead to damage to those obstacles (for example, luggage) and the seat, and thereby reduce the service life of the seat. In order to overcome those disadvantages, the unit for controlling the seat comprises means for controlling the command for each of the actuators.
Such a seat is mechanically modelled by a set of specific points, for example, the free end of the backrest or the footrest, and each specific point is moved in accordance with a previously defined trajectory which is associated therewith and which allows each specific point to avoid the obstacles in order to move from a first to a second predetermined position. Software allows the speed of the or each actuator involved in the movement of the specific point to be controlled so that it best follows the associated trajectory. Each change in predetermined position requires resetting of the associated trajectories.
Although that solution for controlling the actuators prevents some portions of the seat from striking obstacles in an effective manner, the definition of the trajectories is extremely complex to carry out, especially since the seat comprises a large number of movable portions (and as many actuators).
Furthermore, the control of the speed of each actuator involved in the movement of the movable portions of the seat into a predetermined position is continuous because the current position of each specific point of the movable portions must be on the trajectory. Consequently, the current position of each specific point is constantly corrected in order to follow the predetermined trajectory.